Conventionally, as a fuel cell stack as described above, there is one disclosed as a fuel battery in Japanese Patent (Granted) Publication No. 4432518, for example. The fuel battery disclosed in Japanese Patent (Granted) Publication No. 4432518 is one in which a plurality of fuel cells are stacked. The fuel cell includes, on both sides of an MEA (membrane electrode assembly), a hydrogen electrode having a shape with protrusions and depressions in cross-section and an oxygen electrode that includes a drainage layer likewise having a shape with protrusions and depressions in cross-section. It also includes a planar plate separator that respectively forms a hydrogen passage and an oxygen passage between the hydrogen electrode and the oxygen electrode. Furthermore, the fuel cell includes a coolant passage portion on the oxygen electrode side.
The coolant passage portion includes two planar plate separators, a pre-load plate sandwiched between them. The spaces between both planar plate separators are made passages for cooling water. The pre-load plate has a wave-shaped cross-section, and distributes a locally generated load caused by a form error in the component parts of the fuel cell. The load is thereby evenly applied to each of the component parts.